Benjamin D. Young

“I can smell you”—spoken as a factive statement, it is jarring and if uttered to a stranger it seems transgressive. Telling someone you see them generates a sense of affirming their identity, but your smell is private. Perhaps smell isn’t the lead sense, but what I hope to make clear throughout this chapter is that our sense of smell allows us to perceive aspects of our own and other’s identity. The chapter aims to show that our unconscious perception of the smell of ourselves and others partially constitutes the foundations for our sense of self. We are immersed within an invisible sea of odourous chemical currents, some derived from our environment with its everyday flux of objects while other odourous plumes derive from the humanity encompassing us. People have a rich bouquet of smells generated from the volatile chemical compounds emanating from them, including their bodily odours (BO), their adorned perfumes, and associated environmental smells from their abode hitchhiking on their person. As individuals we have a smell that is composed from these ranges of odours that allows us to recognize ourselves as an olfactory entity distinct from someone else’s BO bouquet. However, if forced to introspectively report our own smell we would be befuddled. We aren’t often aware of smelling ourselves (unless we are worried about stinking), and we have trouble recollecting the last time we volitionally engaged in exploratorily sniffing someone else. Thus, establishing a weak constitution relation between smelling and our sense of self is challenging. What will need to be revealed is something that escapes our daily awareness and introspective access, that is, that we are continually perceiving our own and other people’s smells. Moreover, these qualitative states occur outside of conscious awareness and yet generate an underlying aspect of our sense of self. Aside from jostling our intuitions about the foundations of our sense of self the evidence surveyed might also require reconceptualizing the conscious versus unconscious distinction in accommodating the nature of our olfactory self and other smelling.

Our sense of smell pervasively influences our most common behaviors and daily experience, yet little is known about olfactory consciousness. Over the past decade and a half research in both the fields of Consciousness Studies and Olfaction has blossomed, however, olfactory consciousness has received little to no attention. The olfactory systems unique anatomy, functional organization, sensory processes, and perceptual experiences offers a fecund area for exploring all aspects of consciousness, as well as a external perspective for re-examining the assumptions of contemporary theories of consciousness. It has even been suggested that the olfactory system may represent the minimal neuroanatomy that is required for conscious processing. Here, we seek contributions that should serve as the foundation for future research concerning consciousness using olfaction as a model. Given the variegated nature of research on consciousness, we seek original papers including review articles, original research, and theoretical contributions concerning the nature of olfactory consciousness. The scope of the special edition widely incorporates olfaction as it relates to Consciousness, Awareness, Attention, Phenomenal- or Access-Consciousness, and Qualia. Research concerning olfaction and cross-modal integration as it relates to conscious experience is also welcome. As the initial foray into this uncharted area of research, we welcome contributions from across all disciplines contributing to cognitive neuroscience, including neurobiology, neurology, psychology, philosophy, linguistics, and computer sciences. It is our hope that this special edition will serve as the impetus for future interdisciplinary research on olfaction and consciousness.

This carefully designed, multi-authored textbook covers a broad range of theoretical issues in cognitive science, psychology, and neuroscience. With accessible language, a uniform structure, and many pedagogical features, Mind, Cognition, and Neuroscience: A Philosophical Introduction is the best high-level overview of this area for an interdisciplinary readership of students. Written specifically for this volume by experts in their fields who are also experienced teachers, the book’s thirty chapters are organized into the following parts: I. Background Knowledge, II. Classical Debates, III. Consciousness, IV. Crossing Boundaries. Each chapter starts with relevant key words and definitions and a chapter overview, then presents historical coverage of the topic, explains and analyzes contemporary debates, and ends with a sketch of cutting edge research. A list of suggested readings and helpful discussion topics conclude each chapter. This uniform, student-friendly design makes it possible to teach a cohort of both philosophy and interdisciplinary students without assuming prior understanding of philosophical concepts, cognitive science, or neuroscience. Key Features: Synthesizes the now decades-long explosion of scientifically informed philosophical research in the study of mind. Expands on the offerings of other textbooks by including chapters on language, concepts and non-conceptual content, and animal cognition. Offers the same structure in each chapter, moving the reader through an overview, historical coverage, contemporary debates, and finally cutting-edge research. Packed with pedagogical features, like defined Key Terms, Suggested Readings, and Discussion Questions for each chapter, as well as a General Glossary. Provides readers with clear, chapter-long introductions to Cognitive Neuroscience, Molecular and Cellular Cognition, Experimental Methods in Cognitive Neuroscience, Philosophy of Mind, Philosophy of Science, Metaphysical Issues, and Epistemic Issues.　

Any comprehensive theory of smell must account for (1) the distal nature of smells, (2) how smells are represented within odorous experiences, and (3) the olfactory quality of smells. Molecular Structure Theory (MST) and more recent developments arguably provide an account of these questions. It has been argued that we can account for (3) olfactory quality in light of the molecular structure of chemical compounds that compose the odorant plumes which we perceive as (1) distal mereological complex perduring objects within smellscapes. Additionally it has been argued that olfactory perceptual and cognitive processing implements (2) a non-conceptual representational system that is incompatible with the compositional format employed by semantic processing systems. The theory I have been developing generates a comprehensive account of smell by treating these as nested issues inherent in for the nature of smell (Young, 2016, 2019a-d, 2020). However, the chapter assesses the adequacy of my theory by addressing recent criticisms of MST’s account of olfactory quality (Barwich 2014, 2015; Keller 2015, 2017), the need for positing odor objects (Barwich 2019), and a possible incompatibility between my account of synchronic odor perception in MST and more recent developments focusing on the diachronic experiences of smellscapes.

It is arguably the case that olfactory system contains two senses that share the same type of stimuli, sensory transduction mechanism, and processing centers. Yet, orthonasal and retronasal olfaction differ in their types of perceptible objects as individuated by their sensory qualities. What will be explored in this paper is how the account of orthonasal smell developed in the Molecular Structure Theory of smell can be expanded for retronasal olfaction (Young, 2016, 2019a-b, 2020). By considering the object of olfactory perception to be the molecular structure of chemical compounds composing odor plumes, Molecular Structure Theory provides a means for determining an odor’s olfactory quality, how odors can be identified and individuated, and how we perceive smellscapes. Surveying the differences between orthonasal and retronasal olfaction provides the basis for the central argument of the paper that the perceptible objects we refer to as smells and individuated on the basis of their olfactory qualities are only relative to orthonasal olfaction. Retronasal olfaction it is speculatively concluded might play an essential role in our perception of flavorful objects.

Larry Shiner's book is a great exploratory sniff of the aesthetics of smell and the myriad types of odorific arts. Shiner does a fantastic job of introducing those unfamiliar with the subject matter to the use of smells as artwork, as well as their importance within aesthetic experiences across history and cultures. The book offers a pluralist conception of art that makes room for worldwide olfactory aesthetics, drawing on numerous historical and contemporary examples of scent arts, introductory olfactory neuroscience, and careful philosophical analysis with easy-to-follow arguments.

Olfactory perception provides a promising test case for enactivism, since smelling involves actively sampling our surrounding environment by sniffing. Smelling deploys implicit skillful knowledge of how our movement and the airflow around us yield olfactory experiences. The hybrid nature of olfactory experience makes it an ideal test case for enactivism with its esteem for touch and theoretical roots in vision. Olfaction is like vision in facilitating the perception of distal objects, yet it requires us to breath in and physically contact the sensory object in a manner similar to touch. The paper offers an analysis of the central theoretical components of enactivism, whose soundness and empirical viability are tested using the empirical literature on sniffing. It will be shown that even if sniffing is an essential component of olfaction, the motoric component is not necessary for perceiving smells, which is contrary to the most crucial tenet of enactivism. Thus, the paper concludes that the theory cannot account for olfactory perception.

Theoretical Perspective on Smell is the first collection of scholarly articles to be devoted exclusively to philosophical research on olfaction. The essays, published here for the first time, bring together leading theorists working on smell in a format that allows for deep engagement with the emerging field, while also providing those new to the philosophy of smell with a resource to begin their journey. The volume’s 14 chapters are organized into four parts: I. The Importance and Beauty of Smell II. Smell in Time and Space III. What We Perceive through Smell IV. Smell and Other Senses The collection solidifies the area as an important emerging branch of perceptual philosophy by presenting the cutting edge research being done by innovative early career researchers, as well as by those more senior and established within the field. Table of Contents 1. Introduction Andreas Keller and Benjamin Young Part I: The Importance and Beauty of Smell 2. The Role of Smell in Consciousness Barry C. Smith 3. The metacognitive gap: Why we both trust and mistrust our sense of smell Ophelia Deroy 4. Perfumes and the Aesthetic Appreciation of Nature Chiara Brozzo 5. Aesthetics, Olfaction, & Environment Michael Aaron Lindquist Part II: Smell in Time and Space 6. Smell and the Space Between Us Clare Batty 7. The Temporal Structure of Olfactory Experience Keith A. Wilson Part III: What We Perceive through Smell 8. How Biology Perceives Chemistry: A Causal Analysis of the Stimulus in Olfaction and its Implications for Scientific and Philosophical Theorizing Ann-Sophie Barwich 9. The Accuracy Conditions of Olfactory Perception Andreas Keller 10. Maybe We Don't Smell Molecular Structure Benjamin D. Young 11. Stuff & Nonsense: Against Mizrahi on Olfaction Harry Sherwood 12. The Layering of Smell William G. Lycan Part IV: Smell and the Other Senses 13. From Odors to Flavors: Perceptual organization in the chemical senses Becky Millar 14. Seeing and hearing flavors Błażej Skrzypulec 15. Smelling Gustatory Qualities Louise Richardson

Amodal completion is the representation of those parts of the perceived object that we get no sensory stimulation from. While amodal completion is rife and plays an essential role in all sense modalities, philosophical discussions of this phenomenon have almost entirely been limited to vision. The aim of this paper is to examine in what sense we can talk about amodal completion in olfaction. We distinguish three different senses of amodal completion – spatial, temporal and feature-based completion – and argue that all three are present and play a significant role in olfaction.

Unconscious processes are mental states that occur in the absence of subjective awareness. We offer a focused historical survey of the robust debate about the nature of unconscious mental processing, from ancient and medieval theories that allow for bodily functions without subjective awareness to the 20th century acceptance of autonomous unconscious processing. The background introduction culminates with the rise of cognitive science in the latter half of the 20th century, as dual systems theories claimed that the mind had two forms of processing: an unconscious system that is associative, fast, and automatic and a conscious system that performs sequential, deliberative, and slow mental functions. More recently, the “cognitive unconscious” has been discovered to perform most if not all cognitive functions including higher-level cognitive processing, such as addition and subtraction. Despite a rich history of experimental methods and findings, recent criticisms are forcing scientists to reexamine these advancements. We are optimistic that the field will develop novel techniques that answer these criticisms, including measures for studying subjective reports in the absence of subjective awareness of the content of the unconscious state and the act of reporting.

The chapter provides an overview of the structure and content of the textbook to help situate the reader. It begins by introducing this unique collaborative project, including a general introduction to the fields of philosophy, cognitive science, and neuroscience. It then segues into explaining the structural features of each chapter that provide uniformity across the textbook. The chapter concludes with an overview of the content provided in the textbook. Through a survey of the major themes and their interconnections the reader will be better able to appreciate the rich interplay between philosophy and cognitive neuroscience in each of the topical chapters.

Mental Imagery, whereby we experience aspect of a perceptual scene or perceptual object in the absence of direct sensory stimulation is ubiquitous. Often the existence of mental imagery is demonstrated by asking one’s reader to volitionally generate a visual object, such as closing ones eyes and imagining an apple. However, mental imagery also arises in auditory, tactile, interoceptive, and olfactory cases. A number of influential philosophical theories have attempted to explain mental imagery in terms of belief-based forms of representation using the Dependence Thesis, dependence upon means of access, such as enactivism, or in terms of the similarity of content with perceptual processing. The focus of this paper concerns the later approach and in particular assessing if Nanay’s promissory note that his theory is applicable to modalities other than vision, such as smell, seems likely to be of theoretical tender. The thesis argued for in this paper is that olfactory imagery exists and is best accounted for by considering it as a type of perceptual processing with a unique representational format relative to the olfactory perceptual modality. The paper concludes by summarizing the applicability of Nanay’s theory of mental imagery for olfaction and suggests some further issues that arise when transitioning to multi-modal mental imagery.

We perceive smells as perduring complex entities within a distal array that might be conceived of as smellscapes. However, the philosophical orthodoxy of Odor Theories has been to deny that smells are perceived as having a distal location. Recent challenges have been mounted to Odor Theories’ veracity in handling the timescale of olfactory perception, how it individuates odors as a distal entities, and their claim that olfactory perception is not spatial. The paper does not aim to dispute these criticisms. Rather, what will be shown is that Molecular Structure Theory, a refinement of Odor Theory, can be further developed to handle these challenges. The theory is further refined by focusing on distal perception that requires considering the perceptual object as mereologically complex persisting odor against a background scene conceived of as a smellscape. What will be offered is an expansion of Molecular Structure Theory to account for distal smell perception within natural environments.

We are immersed within an odorous sea of chemical currents that we parse into individual odors with complex structures. Odors have been posited as determined by the structural relation between the molecules that compose the chemical compounds and their interactions with the receptor site. But, naturally occurring smells are parsed from gaseous odor plumes. To give a comprehensive account of the nature of odors the chemosciences must account for these large distributed entities as well. We offer a focused review of what is known about the perception of odor plumes for olfactory navigation and tracking, which we then connect to what is known about the role odorants play as properties of the plume in determining odor identity with respect to odor quality. We end by motivating our central claim that more research needs to be conducted on the role that odorants play within the odor plume in determining odor identity.

The chapter unfolds in the following sections. The first section exam- ines the reasons for claiming that olfactory perception is spatially unstruc- tured and our experience of smells has an abstract structure. The second section elucidates the further arguments that olfaction cannot generate figure-ground segregation. The third section assesses the conclusion that olfactory perception and experience cannot solve the MPP. Following the overview of the many problems inherent to distal olfactory percep- tion, MST will be introduced as an alternative perspective that allows for figure-ground segregation and perceiving multiple olfactory objects within an array. The chapter then concludes by replying to the shared argument that olfactory distal perception does not have the requisite res- olution to resolve the many properties problem.

There is consensus within the chemosciences that olfactory perception is of the molecular structure of chemical compounds, yet within philosophical theories of smell there is little agreement about the nature of smell. The paper critically assesses the current state of debate regarding smells within philosophy in the hopes of setting it upon firm scientific footing. The theories to be covered are: Naïve Realism, Hedonic Theories, Process Theory, Odor Theories, and non-Objectivist Theories. The aforementioned theories will be evaluated based on their explanations of the (a) the olfactory quality of a smell, (b) smells as distal entities, and (c) our experience of smells as intentional objects. The paper concludes with a defense of Molecular Structure Theory that demonstrating its superiority in accounting for each of these three aspects of smell.

Quality-space theory (QST) explains the nature of the mental qualities distinctive of perceptual states by appeal to their role in perceiving. QST is typically described in terms of the mental qualities that pertain to color. Here we apply QST to the olfactory modalities. Olfaction is in various respects more complex than vision, and so provides a useful test case for QST. To determine whether QST can deal with the challenges olfaction presents, we show how a quality space (QS) could be constructed relying on olfactory perceptible properties and the olfactory mental qualities then defined by appeal to that QS of olfactory perceptible properties. We also consider how to delimit the olfactory QS from other modalities. We further apply QST to the role that experience plays in refining our olfactory discriminative abilities and the occurrence of olfactory mental qualities in non-conscious olfactory states. QST is shown to be fully applicable to and useful for understanding the complex domain of olfaction.

Qualitative-consciousness arises at the sensory level of olfactory processing and pervades our experience of smells to the extent that qualitative character is maintained whenever we are aware of undergoing an olfactory experience. Building upon the distinction between Access and Phenomenal Consciousness the paper offers a nuanced distinction between Awareness and Qualitative-consciousness that is applicable to olfaction in a manner that is conceptual precise and empirically viable. Mounting empirical research is offered substantiating the applicability of the distinction to olfaction and showing that olfactory qualitative-consciousness can occur without awareness, but any olfactory state that we are aware of being in is always qualitative. Evidence that olfactory sensory states have a qualitatively character in the absence of awareness derives from research on mate selection, the selection of social preference for social interaction and acquaintances, as well as the role of olfactory deficits in causing affective disorders. Furthermore, the conservation of secondary processing measures of olfactory valence during olfactory imagery experiments provides verification that olfactory awareness is always qualitatively conscious—all olfactory consciousness smells phenomenal.

Although vision is the de facto model system of consciousness research, studying olfactory consciousness has its own advantages, as this collection of articles emphatically demonstrates. One advantage of olfaction is its computational and phenomenological simplicity, which facilitates the identification of basic principles. Other researchers study olfactory consciousness not because of its simplicity, but because of its unique features. Together, olfaction's simplicity and its distinctiveness make it an ideal system for testing theories of consciousness. In this research topic, the results of recent research into olfactory consciousness are presented.

Contemporary neuroscientific theories of consciousness are typically based on the study of vision and have neglected olfaction. Several of these (e.g. Global Workspace Theories, the Information Integration theory, and the various theories offered by Crick and Koch) claim that a thalamic relay is necessary for consciousness. Studies on olfaction and the olfactory system's anatomical structure show this claim to be incorrect, thus showing these theories to be either false or inadequate as general and comprehensive accounts of consciousness. Attempts to rescue these theories by claiming that there is a structure in the olfactory system that is functionally equivalent to the thalamus in the visual system, such as the olfactory bulb or the olfactory cortex, are also shown to fail. If we wish to understand consciousness, we have to wake up and smell it.

The olfactory system processes smells in a structural manner that is unlike the composition of thoughts or language, suggesting that some of the content of our olfactory experiences are represented in a format that does not involve concepts. Consequently, formative non-conceptual content is offered as an alternative theory of non-conceptual content according to which the difference between conceptual and non-conceptual states is simply a matter of the format of their structural parts and relations within a system of representations. Aside from the theoretical merits of rethinking the quagmire of a debate regarding non-conceptual content as a format issue, studying olfaction shows that formative non-conceptual content is empirically plausible.

While the objects of olfaction are intuitively individuated by reference to the ordinary objects from which they arise, this intuition does not accurately capture the complex nature of smells. Smells are neither ordinary three-dimensional objects, nor Platonic vapors, nor odors. Rather, smells are the molecular structures of chemical compounds within odor plumes. Molecular Structure Theory is offered as an account of smells, which can explain the nature of the external object of olfactory perception, what we experience as olfactory objects, and what determines the olfactory quality of smells by which we can demarcate the spatiotemporal boundaries of smells